Avalanche Photodiodes (APD) are mainly used in applications where high sensitivity is desired. Such applications include long haul fiber-optic telecommunication, laser rangefinder, and single photon level detection and imaging, among other applications. SiGe APD offers promising applications targeted at near-infrared optical signals. In a Si/Ge separate absorption, charge and multiplication (SACM) APD, Germanium (Ge) offers high responsivity at near-infrared wavelengths, while Silicon (Si) is used to amplify the generated photocarriers with low noise.
In addition, the applicability of CMOS technology to the fabrication of SiGe based APDs promises reduced prices compared to its III-V APD counterparts. Since APDs have traditionally targeted high-end markets mainly due to higher cost constraints, SiGe APD is a promising candidate for low end markets that require high sensitivity in the near infrared spectrum.
However, reduced price alone is insufficient to realize the widespread application of APDs. The biggest obstacle is the high bias required for the operation of APDs, which in the conventional art operate far beyond the maximum available bias of 12 V found within modern electronics such as server, desktop, and other consumer electronics.
Accordingly, it would be desirable to reduce the operating bias, or breakdown bias, of Si/Ge APDs so that they can be successfully incorporated into consumer electronics, high speed communication networks, and the like.